After quickly skim reading it seems I'm the only one who thinks what I think.

Boulder doesn't exist.

It was something Puck said last episode. (think it was Puck anyways) he said if the outbreak happened a week later there would have been a battalion of infantry on the base. But he then muttered 'more mouths to feed' if you had a secure population centre of 150k that from what Carl was saying to the guys seems to be secure and pumping out food surely the extra trained soldiers would have been more than welcome?

Therefore, I think, probably incorrectly, that boulder doesn't exist, all survivors are given a choice, join up and fight, or go to boulder that doesn't exist and they are probably just left in a field to be eaten. After all if all your population are soldiers you stand a much better chance of defeating the outbreak than having most of your forces defending civilians.

I never used to be so cynical, must be Kc's doing!